Bacterial Dissociation

Braun, Werner

doi:10.1128/mmbr.11.2.75-114.1947

Cited by 20 publications

(5 citation statements)

References 70 publications

(97 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Rough Brucella organisms are characterized by a defect in O-antigen presentation and arise spontaneously in cultures in a process classically referred to as dissociation or, perhaps more appropriately, smooth-to-rough phase variation (6,25). Several environmental factors, including nutrient availability, temperature, and aeration, have been shown to influence the rate of appearance of rough Brucella organisms in culture (5).…”

mentioning

confidence: 99%

Transposon-Derived Brucella abortus Rough Mutants Are Attenuated and Exhibit Reduced Intracellular Survival

1998

View full text Add to dashboard Cite

The O antigen of Brucella abortus has been described as a major virulence determinant based on the attenuated survival of fortuitously isolated rough variants. However, the lack of genetic definition of these mutants and the virulence of naturally occurring rough species, Brucella ovis and Brucella canis, has confused interpretation. To better characterize the role of O antigen in virulence and survival, transposon mutagenesis was used to generate B. abortus rough mutants defective in O-antigen presentation. Sequence analysis of DNA flanking the site of Tn5 insertion was used to verify insertion in genes encoding lipopolysaccharide (LPS) biosynthetic functions. Not surprisingly, each of the rough mutants was attenuated for survival in mice, but unexpected differences among the mutants were observed. In an effort to define the basis for the observed differences, the structure of the rough LPS and the sensitivity of these mutants to individual killing mechanisms were examined in vitro. All of the B. abortus rough mutants exhibited a 4- to 5-log-unit increase, compared to the smooth parental strain, in sensitivity to complement-mediated lysis. Little change was evident in the sensitivity of these organisms to hydrogen peroxide, consistent with an inability of O antigen to exclude relatively small molecules. Sensitivity to polymyxin B, which was employed as a model cationic, amphipathic peptide similar to defensins found in phagocytic cells, revealed survival differences among the rough mutants similar to those observed in the mouse. One mutant in particular exhibited hypersensitivity to polymyxin B and reduced survival in mice. This mutant was characterized by a truncated rough LPS. DNA sequence analysis of this mutant revealed a transposon interruption in the gene encoding phosphomannomutase (pmm), suggesting that this activity may be required for the synthesis of a full-length core polysaccharide in addition to O antigen. B. abortus O antigen appears to be essential for extra- and intracellular survival in mice.

show abstract

mentioning

confidence: 99%

Transposon-Derived Brucella abortus Rough Mutants Are Attenuated and Exhibit Reduced Intracellular Survival

1998

View full text Add to dashboard Cite

show abstract

“…Some of the present methodology for distinguishing species among these genera of lactic acid bacteria should be studied and improved. According to Braun (1947), "An improved method of classification would involve the description of the total potential mutational range of each bacterial species." However, as Braun has stated, the method would be too cumbersome for practical purposes.…”

Section: Discussionmentioning

confidence: 99%

Variation Among the Heterofermentative Lactic Acid Bacteria

Pederson

Albury

1955

J Bacteriol

View full text Add to dashboard Cite

show abstract

“…Selection may also act at the end of growth. If both components have ceased to grow, a shift in proportion may occur through differential viability (Braun, 1947;Witkin, 1947). Or in the absence of such a differential, if one of the components ceases growth before the other, the final population will differ from the inoculum.…”

Section: Discussionmentioning

confidence: 99%